Saving money related to a 928 sometimes doesn't seem worth the effort, but at least its a cheap hobby. Rubber parts need extra caution because quality issues may not immediately be apparent, and its no fun to have rubber parts start cracking etc. a few months after installation.
http://www.metrommp.com/ makes replacement trim parts, but generally I think they are seen as less than OEM quality.
Like it or not, the more rubber I pull off my parts car, the more rubber I see as essential to have replaced with new during a paint job or any other time its removed.
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The window inner and outer seals, the squeegee at the bottom of the glass, is a funky shape to fit into the body channel that holds it, but its straight so it might be possible to extrude a decent replacement.